Polymer-cladded athermal high-index-contrast waveguides

Publication

Publication

We present a general approach to design temperature-independent high-index-contrast (HIC) waveguides using polymer claddings. Thermal stability has been a significant issue in electronic-photonic integrated circuits because of the heterogeneous heating resulting from integration with electronics. Due to silicons highly temperature-dependent optical properties, athermal performance in silicon-based devices is the critical limitation in device performance. In applications such as wavelength demultiplexing (WDM) and high-resolution spectroscopy, the thermo-optic (TO) effect results in a wavelength shifts and phase shifts in the spectral response peak of each wavelength channel, which limits the wavelength resolution and affects the spectral channel density. Instead of attempting to diminish temperature gradience across the chip, an elegant solution is to design athermal waveguides that are insensitive to ambient temperature. Thermo-optically neutral designs are achieved by choosing a polymer cladding material, whose thermo-optic coefficient is opposite to that of silicon (TOSi = +1.8×10-4 K-1). We present a comprehensive study of temperature dependence in HIC waveguides, using DuPont's polymers as the cladding materials. We provide general design criteria for athermal HIC waveguides by developing analytical and empirical expressions.